1. Field of the Invention
This invention concerns inductive components, of the type including one or more windings, and which can be used therefore depending on case as inductors or alternating current transformers. Such components, as inductors, are generally used to perform in electric or electronic circuits the filtering, smoothing or energy storage functions, being conventionally traversed by currents with a DC component on which an AC component is superimposed. A current operating frequency range is 10 kHz to 3 MHz. Such components are for instance currently used in switched power supplies or DC converters. Also, these components are conventionally made so that they can be installed on printed circuits in a manner known itself.
2. Description of the Related Art
Known inductors of the type mentioned above generally consist of one or more enamelled copper wire windings made on a toroidal core supported by a base including connecting pins. Conventionally, especially to reduce the overall surface area on the printed circuit, the toroidal windings are arranged vertically on the base so as to extend perpendicularly to the surface of the printed circuit. The ends of the wires are connected to the connecting pins or themselves form the said pins which are intended to be inserted into holes drilled in the printed circuit or soldered to it in a conventional manner. Although it is possible to also adopt a surface-mounted component (SMC) type design which is more suited to automatic installation, the high volume and weight of these components generally prohibits such a design and these components must be mounted manually on the printed circuit before soldering. Also, the mechanical strength in cases of strong vibrations is not very reliable on account of the high weight and the relative distance of the core from the printed circuit when compared with the relatively small dimensions of the base.
Moreover, the magnetic materials used for the toroidal core are generally iron powder based, for example, iron-silicon, when the planned operating frequencies are low, up to 100 kHz, or when the frequencies are higher, up to 200 kHz, made of a ferronickel alloy such as permalloy, for instance the material currently known under the name of Moly-Permalloy or MPP, which is a sintered iron and nickel powder with 80 or 50% nickel.
These two materials have the advantage of supporting a high DC magnetic field which enables the section of the core, and therefore the overall size of the component to be reduced.
However, their losses are high when used at high frequencies, that is around several hundred kHz to several MHz and therefore are poorly suited to uses such as in converter switching power supply circuits which increasingly use very high frequencies.
Another disadvantage of toroidal-type windings is that they are not sealed, the wire being simply wound around the toroidal core without external protection.